Broadcast - Takes data from multiple inputs, combines it and sends it to all the output ports.

Eg - You have 2 incoming flows (This can be data parallelism or component parallelism) on Broadcast component, one with 10 records & other with 20 records. Then on all the outgoing flows (it can be any number of flows) will have 10 + 20 = 30 records

Replicate - It replicates the data for a particular partition and send it out to multiple out ports of the component, but maintains the partition integrity.

Eg - Your incoming flow to replicate has a data parallelism level of 2. with one partition having 10 recs & other one having 20 recs. Now suppose you have 3 output flos from replicate. Then each flow will have 2 data partitions with 10 & 20 records respectively.